AbstractThe work embodied in this dissertation is mainly concerned with the isolation and characterization of chemical constituents from a terrestrial plant. The isolated compounds whether new or previously reported in the literature, were characterized by using various sophisticated spectroscopic techniques available at this institute.

The dissertation is divided in two parts dealing with the chemistry of Stocksia brauhica. In Part A the chemical analysis of fruits of Stocksia brauhica is described. Part B deals with the chemical analysis of petals of Stocksia brauhica (Sapindaceae).

Chemical analysis of fruits of Stocksia brauhica The studies on fruits resulted in the isolation and characterization of five new constituents, out of these, one compound contain oleanane glycoside skeleton and four have flavonoid glycoside skeleton. In addition to these new constituents, four known compounds have also been isolated and identified from this species. The new constituents isolated from fruits include: brauenesaponin A (54), brauhenefloroside C (55), brauhenefloroside 0 (56), brauhenefloroside E (57) and brauhenefloroside F (58).

The known compounds isolated from the fruits are oleanolic acid (50), lupeol (51), β-sitosterol (52) and β-sitosterolglycoside (53).

Compounds 57 and 58 were subjected to radical scavenging assay to evaluate the antioxidant potential using two complimentary assays, DPPH (1,1-Diphenyl-2-picrylhydrazyl radical) scavenging assay and NO (Nitric oxide radical) scavenging assay. Both of these compounds were inactive against DPPH and having moderate activity against NO.

Chemical analysis of petals of Stocksia brauhica Part-B deals with the chemical studies on S. brauhica. The present work has resulted in the isolation of three known compounds. These compounds include, 3-0-glucose-3',4',S,7-tetrahydroxyflavone (59), 3-0-rutinosyl-4',S,7,trihydroxy flavone (60), 3-0-rutinosyl-3',4',S,7-tetrahydroxy flavone (61). Compound 60 and 61 were subjected to radical scavenging assay to evaluate the antioxidant potential of test samples using two complimentary in vitro bioassays, DPPH (l,1-Diphenyl-2-picrylhydrazyl radical) scavenging assay and NO (Nitric oxide radical) scavenging assay. Both these compounds are active against DPPH and NO.